1. Field of the Invention
The present invention relates to a refrigerating cycle with a by-pass duct capable of using an evaporator, which usually is used for cooling purposes, for auxiliary heating as required. The refrigerating cycle preferably is intended for an automobile.
In an automotive air-conditioner a general refrigerating cycle is used for cooling purposes while an engine refrigerating cycle is used for cooling the engine and heating cooling water of the engine which cooling water when heated is used for heating e.g. the passenger compartment. However, recent engine developments resulted in engines with improved efficiency, for example gasoline injection type engines and direct injection diesel engines, in which the temperature of the cooling water does not rise as high as in the past. This leads to the inconvenience that particularly in winter time the heating temperature or heating capacity is no more sufficient for the passenger compartment.
2. Description of the Related Art
EP-A-0197839 corresponding to U.S. Pat. No. 4,893,748 relates to a heating method using an air-conditioner provided on board of a vehicle and comprising at least a compressor and an evaporator wherein the total or a part of the fluid is derived from the air-conditioning circuit after compression and then re-injected after pressure relief at the inlet of the evaporator in order to gain in a heating operational mode of said air-conditioner additional heating capacity for the passenger compartment. The structure of said heating device actually constituted by the slightly modified air-conditioner of conventional design includes an element for deriving a discharge fluid of the compressor towards a depression element for re-heating the atmospheric airflow across the evaporator prior to the entry of the atmospheric airflow into the cabin. Said depression element is able to deviate the condenser, the fluid receiver and the expansion valve of the air-conditioner by means of a by-pass duct connecting the exit of the compressor and the inlet of the evaporator. Said by-pass duct contains a depression element insuring an isoenthalpic pressure relief e.g. in the form of a flow rate regulator alone or in association with at least one additional parallel jet nozzle or including a jet nozzle having an adjustable flow section. In order to raise the heating efficiency a preheating device can be provided either in the airflow entering the evaporator or for preheating a buffer tank located downstream the condenser and/or the evaporator itself.
A climatization system of an automobile as known from DE A 3635353 is equipped with an additional heat exchanger located downstream of the main evaporator and upstream of an accumulator in front of the suction side of the compressor. Within the main circuit passing the condenser a by-pass duct is branching off to a junction in the main circuit located downstream the expansion valve situated downstream of the condenser. A further by-pass duct is connecting the exit of the evaporator and said accumulator and contains a motor-driven on/off-valve. The additional heat exchanger is also passed by the cooling medium of the engine. Upstream of said additional heat exchanger an additional expansion valve is provided. In the cooling mode said first by-pass duct and said second expansion valve and the heat exchanger are isolated. In the heating mode said second by-pass duct and the condenser with its downstream expansion valve are isolated. The airflow entering the passenger compartment is passing the evaporator. Said second heat exchanger is functioning as an additional evaporator for the refrigerant in the heating mode.
An air-conditioner as know from U.S. Pat. No. 5,291,941 is structurally modified for a heating mode by a by-pass duct deviating the condenser, a receiver, a check valve and an expansion valve all located downstream of said condenser, and is connecting the exit of the compressor with the inlet of the evaporator. Said by-pass duct is containing an on/off valve and a heating expansion valve. Between the evaporator and the inlet of the compressor an accumulator is provided. The evaporator is situated within an air duct to the passenger compartment upstream of a heater core connected to the engine and passed by the cooling water.
A further automotive air-conditioner known from FR A 2720982, FIG. 2, is functionally similar represented as a schematic block diagram in FIG. 9 of this application. A by-pass duct 5 is placed in juxtaposition to supply high-pressure refrigerant gas supplied from compressor 1 of the refrigerating cycle to an evaporator 4 within a car room with-out passing the refrigerant in the heating mode through condenser 2 provided outside the car room, for performing heat exchange by taking sensibly heat from the evaporator or, as an auxiliary heating. The refrigerating cycle of this conventional design contains an expansion valve 3, a liquid tank 10 for temporarily storing high-pressure refrigerant liquid, a check valve 7 between liquid tank 10 and expansion valve 3, a duct selector valve 8 for guiding high-pressure refrigerant delivered by the compressor 1 either to condenser 2 or to deviate it (heating mode) via by-pass duct 5. A constant differential pressure regulating valve 9 is situated in by-pass duct 5 which operates as expansion valve when the refrigerant flows through the by-pass duct 5. In the above described, conventional refrigerating cycle the amount of the refrigerant to be circulated becomes constant, since the refrigerant does not pass through the liquid tank 10 during the auxiliary heating mode. As a consequence, the amount of the refrigerant cannot be controlled in response to the load and the like. Therefore, heating cannot be performed in accordance with the conditions.